The role of excess As in low-temperature (LT) grown Be doped, undoped and Si-doped GaAs subjected to BCl3/Ar reactive ion etching has been investigated using transmission electron microscopy and atomic force microscopy. Etching rate and the extent of ion damage are found to depend on the doping type and thermal treatment. For as-grown LT-GaAs, significant decrease in etching rate is observed as the dopant is changed from Be to Si. Thermal treatment by rapid thermal annealing slightly increases the etching rate of GaAs grown at low temperature while it increases the etching rate significantly for the samples grown at normal temperature. In addition, as-grown LT-GaAs also exhibits superior resistance to the ion damage of reactive ion etching. (C) 1999 American Institute of Physics. [S0003-6951(99)03345-8].